1. Field of the Invention
The present invention relates to a light-emitting device using a light-emitting transistor.
2. Description of the Related Art
Since light-emitting devices using light-emitting elements as display elements have high visibility, are suitable for reduction in thickness, and have a wide viewing angle, they have attracted attention as display devices which can take the place of cathode ray tubes (CRTs) or liquid crystal display devices. In particular, a light-emitting element having a transistor structure, which is called a light-emitting transistor, has both a function of a light-emitting element and a function of a transistor. Therefore, a light-emitting device including a light-emitting transistor in a pixel has a higher aperture ratio than a light-emitting device including both a light-emitting element and a transistor which controls a current supplied to the light-emitting element in a pixel. In addition, compared to the case of manufacturing both a transistor and a light-emitting element, fewer elements are needed to be formed in a light-emitting device using a light-emitting transistor; therefore, a light-emitting device using a light-emitting transistor is advantageous also in the yield and manufacturing cost of products.
Reference 1 (PCT International Publication No. 03/071608) and Reference 2 (Japanese Published Patent Application No. 2006-252774) each discloses a specific structure of a light-emitting transistor.